The present invention pertains to methods and systems for service domain selection, and more particularly to methods and systems for wireless cellular systems.
In the third generation mobile telephone communication systems that are being defined by various standardization bodies, two distinct switch domains have been identified for the networks servicing user equipment (UE). These domains are the circuit switched (CS) service domain and the packet switched (PS) service domain. In the circuit switch domain signals are physically routed to the appropriate destination through a unique connection whereas in the packet switch domain message packets are routed to the appropriate destination based on addresses in the packet. These domains are distinct and are implemented using different equipment.
One problem encountered designing third generation (3G) cellular networks is accommodating user equipment services implemented in both the circuit switch and packet switch domains. The first releases of third generation standards specify implementing services in both domains. Furthermore, the services offered by the access network to all core network domains in 3G systems are the same. Given that real time services are migrating from circuit switched networks to packet switched networks in wire-line telecommunications, it appears that a similar migration must be supported in cellular networks. For example, it is expected that certain services such as conventional cellular speech are likely to be offered initially in the circuit switched domain and later in the packet switched domain.
Additionally, the third Generation Partnership Project (3GPP) proposed architecture has a well-defined separation between the access stratum (AS) and the non-access stratum (NAS). The mobile and network portion of the access stratum does not inspect or manipulate the contents of the non-access stratum message. The non-access stratum portion of a message in the mobile to network direction uses a core network (CN) domain identifier. However, the mobile, or user equipment, does not know the core network architecture, and therefore does not know whether there are one or two domains, or what services are available, and more particularly what services are available in each domain. As a consequence, the mobile is forced to support a predetermined mapping of services to domains; such as all speech messages are mapped to the circuit switch domain. This limits the ability of the overall system to handle calls and support services in an optimum and easily upgradeable manner.
The 1999 release (R99) of the third generation partnership project (3GPP) provides hooks for the mobile to address messages to a specific domain. Additionally, this release acknowledges that there may be a migration of some services from the circuit switch-domain to the packet switch-domain, and that there should be flexibility to support this migration that is compatible with previous systems. However, processes for the transparent migration of services and applications between domains are not specified.
It has been proposed to add a new information element, which is a core network domain indicator, to the access stratum part of the radio resource control (RRC) messages to indicate to which core network a message belongs. In the downlink, the serving radio network controller (SRNC) would insert this information element into the access stratum portion of the radio resource control direct transfer message. In the uplink, the user equipment would insert this information element into the access stratum portion of the radio resource control, enabling the serving radio network controller to decide to which domain the non-access stratum direct transfer message should be routed. However, such an arrangement does not support flexibility.
What is needed is a system for accommodating migration between the circuit switch and packet switch domains that is more flexible.